JP7292188B2 - Aluminous substrate tube with excellent film-forming properties and filtration separation properties - Google Patents
Aluminous substrate tube with excellent film-forming properties and filtration separation properties Download PDFInfo
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Description
本発明は、無機濾過分離膜を用いたフィルター用の、優れた製膜性及び濾過分離特性を有するアルミナ質基体管に関する。 TECHNICAL FIELD The present invention relates to an alumina substrate tube having excellent membrane formability and filtration and separation properties for filters using inorganic filtration and separation membranes.
近年、環境問題が深刻化し、上下水道の水処理や有毒性の有機溶剤の処理に色々な方法が採用されている。しかしどの方法もコストがかかり、特に従来採用されている有機濾過分離膜を用いる方法は、膜が水等で膨潤したり、腐食による濾過分離性能の低下等によって寿命が短くなり交換頻度が高くなるため、結果的にコスト増につながっている。そこで耐食性や耐熱性に優れたセラミックス製の無機濾過分離膜の採用が急増しているが、有機濾過分離膜に比べてコストが高く、コストに見合った濾過分離性能は得られていない。
セラミックス製の無機濾過分離膜は、セラミックス製の多孔質基体管の表面に製膜してフィルターとしての機能を発揮させる。したがって、優れた濾過分離性能を有する必要があることは当然であるが、濾過分離膜で分離した液体や気体を効率よく外部へ排出させることができる濾過分離能力の優れた基体管も重要である。更に基体管の表面に製膜する濾過分離膜の均一性によっても濾過分離能力が大きく変わるので、製膜後の濾過分離膜の状態も重要であり、そのため膜本来の特性を引き出すことができる製膜性に優れる基体管が必要不可欠である。基体管の気孔分布がシャープでない場合には、気孔径が大きい個所と小さい個所で製膜後の濾過分離膜の膜厚に差が生じ、結果的に各部分での濾過分離能力にバラツキが生じて、フィルターとしての濾過分離安定性が得られないことになる。
In recent years, environmental problems have become more serious, and various methods have been adopted for water treatment in water supply and sewage systems and treatment of toxic organic solvents. However, all methods are costly, and in particular, the method using an organic filtration separation membrane, which has been conventionally adopted, has a short life and high replacement frequency due to swelling of the membrane with water or deterioration of filtration separation performance due to corrosion. As a result, it leads to an increase in costs. Therefore, the adoption of inorganic filtration and separation membranes made of ceramics with excellent corrosion resistance and heat resistance is rapidly increasing, but the cost is higher than that of organic filtration and separation membranes, and filtration and separation performance commensurate with the cost has not been obtained.
The inorganic filtration separation membrane made of ceramics is formed on the surface of the porous substrate tube made of ceramics to exhibit its function as a filter. Therefore, it is of course necessary to have excellent filtration separation performance, but it is also important to have a substrate tube with excellent filtration separation performance that can efficiently discharge the liquid or gas separated by the filtration separation membrane to the outside. . Furthermore, the uniformity of the filtration and separation membrane formed on the surface of the substrate tube greatly affects the filtration and separation ability. A substrate tube with excellent film properties is essential. If the pore distribution of the substrate tube is not sharp, there will be a difference in the film thickness of the filtration/separation membrane after film formation between areas with large pore diameters and areas with small pore diameters, resulting in variations in filtration and separation performance in each area. Therefore, filtration separation stability as a filter cannot be obtained.
特許文献１には、気孔率、水銀圧入法で測定した気孔径及びバブルポイント法で測定した気孔径を特定の範囲内とすることにより、機械的特性、気体透過量及び透水量に優れ、良好な製膜性を実現できるアルミナ質からなる基体管の発明が開示されている。しかしながら、この発明は「従来の基体管より広い気孔径分布を示す」とあるように、気孔径分布を広くすることで気体透過量及び透水量を大きくしているに過ぎず、それに伴う気孔径のバラツキによる濾過分離能力への影響については全く考慮していない。
また特許文献２には、バブルポイント法で測定した貫通気孔のモード径と最大貫通気孔径、気孔率及び表面粗さを特定の範囲内にすることにより、良好な製膜性及び濾過分離能力を実現させたアルミナ質からなる基体管の発明が開示されている。しかしながら、この発明も特許文献１の発明と同様に気孔径分布を広くすることにより透水量を大きくすることを意図して、粉砕した粉体の粒度分布を広くさせる方法や粗い粉体と細かい粉体を混合して粒度分布をコントロールする方法を採用しているだけであり、気孔径のバラツキ等による濾過分離能力への影響については全く考慮していない。
更に、従来のアルミナ質からなる基体管の製造では精密に整粒された電融アルミナ粉体を用いることが多いが、コストが高くなるし、粒度を段階的に細かくして多層にした基体管でないと製膜し難い等の問題点があった。
In Patent Document 1, by setting the porosity, the pore diameter measured by the mercury intrusion method, and the pore diameter measured by the bubble point method within a specific range, the mechanical properties, the gas permeation amount, and the water permeation amount are excellent and good An invention of a substrate tube made of alumina that can realize excellent film-forming properties is disclosed. However, the present invention merely increases the gas permeation amount and the water permeation amount by widening the pore size distribution, as described in the description that "the pore size distribution is wider than that of the conventional base tube". No consideration is given to the influence on the filtration separation ability due to the variation in .
Further, in Patent Document 2, by setting the mode diameter and maximum through-hole diameter of through-pores measured by the bubble point method, the porosity and the surface roughness within specific ranges, good membrane formability and filtration separation ability are achieved. Disclosed is an invention of a substrate tube made of an alumina material that has been realized. However, this invention also intends to increase the water permeability by widening the pore size distribution in the same manner as the invention of Patent Document 1, and has a method of widening the particle size distribution of the pulverized powder and a method of mixing coarse powder and fine powder. It merely adopts a method of controlling the particle size distribution by mixing the particles, and does not take into account the influence of variations in pore size, etc., on the filtration and separation ability.
Furthermore, in the conventional manufacture of substrate tubes made of alumina, precisely sized electrofused alumina powder is often used. Otherwise, there are problems such as difficulty in forming a film.
本発明は前記従来技術の問題点を解決すべくなされたものであって、無機濾過分離膜を用いたフィルター用の、優れた製膜性及び濾過分離特性を有するアルミナ質基体管の提供を目的とする。 SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and it is an object of the present invention to provide an alumina substrate tube having excellent film-forming properties and filtration separation characteristics for filters using inorganic filtration and separation membranes. and
本発明者らは鋭意研究を重ねた結果、アルミナ質基体管の表面に無機濾過分離膜を製膜する際に、基体管の気孔率や濾過分離能力（例えば純水透過流束）が高ければ良いわけではなく、基体管の各部分で気孔率及び気孔径を均一にして、基体管のどの部分でもバラツキがなく安定した濾過分離能力を有するようにしないと、無機濾過分離膜を製膜してフィルターとして用いても、濾過分離抵抗及び濾過分離能力の安定性に欠けるため、結果的に安定した濾過分離性能（濾過精度や分離能力など）を有するフィルターは得られないこと、また基体管の気孔径分布がシャープであれば、基体管の表面に製膜した無機濾過分離膜の膜厚及び膜孔径が均一となり、膜本来の特性を有する優れた濾過分離性能を有するフィルターが得られることから、貫通気孔のモード径及び該モード径と最大貫通気孔径や最小貫通気孔径とのバランスも非常に重要であって、可能な限り気孔径を均一にする必要があることを見出した。
そして、更に研究を重ねた結果、後述する要件（ａ）～（ｇ）を満たせば、無機濾過分離膜を用いたフィルター用の、優れた製膜性及び濾過分離特性を有するアルミナ質基体管が得られることを見出し、本発明を完成するに至った。
即ち、上記課題は、次の（１）の発明によって解決される。
As a result of intensive research by the present inventors, when forming an inorganic filtration separation membrane on the surface of an alumina substrate tube, if the substrate tube has a high porosity and filtration separation ability (for example, pure water permeation flux) Unless the porosity and pore size are uniform in each part of the substrate tube so as to have a stable filtration separation ability without variation in any part of the substrate tube, an inorganic filtration separation membrane cannot be formed. Even if it is used as a filter, it lacks the stability of filtration separation resistance and filtration separation ability, and as a result, a filter having stable filtration separation performance (filtration accuracy, separation ability, etc.) cannot be obtained. If the pore size distribution is sharp, the film thickness and membrane pore size of the inorganic filtration separation membrane formed on the surface of the substrate tube will be uniform, and a filter having excellent filtration separation performance with the inherent characteristics of the membrane can be obtained. Furthermore, it was found that the mode diameter of the through pores and the balance between the mode diameter and the maximum or minimum through pore diameter are also very important, and it is necessary to make the pore diameter as uniform as possible.
As a result of further research, if the requirements (a) to (g) described later are satisfied, an alumina base tube having excellent film-forming properties and filtration separation characteristics for filters using inorganic filtration separation membranes is produced. The present inventors have found that it can be obtained, and have completed the present invention.
That is, the above problems are solved by the following invention (1).
（１） 次の要件（ａ）～（ｇ）を満たすことを特徴とする無機濾過分離膜を用いたフィルター用のアルミナ質基体管。
（ａ）Ａｌ２Ｏ３の含有量が８３．０～９４．０重量％
（ｂ）ＳｉＯ２の含有量が５．０～１４．０重量％、アルカリ金属酸化物及びアルカリ
土類金属酸化物の含有量が１．０～３．５重量％、「ＳｉＯ２含有量／アルカリ
金属酸化物及びアルカリ土類金属酸化物の含有量」が２．０～６．０
（ｃ）気孔率が３０～５０％
（ｄ）バブルポイント法で測定した貫通気孔のモード径が０．２０～０．６０μｍ
（ｅ）バブルポイント法で測定した最大貫通気孔径／モード径が５．０以下、
かつ、最小貫通気孔径／モード径が０．５以上
（ｆ）基体管断面における直径３０～８０μｍの粗大気孔が５個／ｍｍ２以下
（ｇ）液圧０．１ＭＰａで透水させた時の純水透過流束が３０～６０ｍ３／ｍ２／ｄａ
ｙ
(1) An alumina substrate tube for a filter using an inorganic filtration separation membrane, which satisfies the following requirements (a) to (g).
(a) Al 2 O 3 content is 83.0 to 94.0% by weight
(b) the content of SiO 2 is 5.0-14.0% by weight, the content of alkali metal oxides and alkaline earth metal oxides is 1.0-3.5% by weight, "SiO 2 content/ The content of alkali metal oxides and alkaline earth metal oxides” is 2.0 to 6.0
(c) Porosity is 30 to 50%
(d) The mode diameter of through pores measured by the bubble point method is 0.20 to 0.60 μm
(e) the maximum through-hole diameter/mode diameter measured by the bubble point method is 5.0 or less;
and the minimum through pore diameter/mode diameter is 0.5 or more (f) The number of coarse pores with a diameter of 30 to 80 μm in the cross section of the substrate tube is 5/mm 2 or less Water permeation flux is 30-60m 3 /m 2 /da
y
本発明によれば、無機濾過分離膜を用いたフィルター用の、優れた製膜性及び濾過分離特性を有するアルミナ質基体管を提供できる。また、本発明のアルミナ質基体管は、アルミナ、シリカ、ゼオライト等のセラミックからなる無機濾過分離膜用の基体管として広く利用できる。更に、容易に入手できる安価なアルミナ原料粉体を用いることができる上に、該原料粉体に焼結助剤を加えて作製した粉砕・分散スラリー中の粒子の平均粒子径や粒度分布を制御するという方法で製造できるので、産業上非常に有用である。 INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an alumina substrate tube having excellent film formability and filtration and separation properties for filters using inorganic filtration and separation membranes. Further, the aluminous substrate tube of the present invention can be widely used as a substrate tube for inorganic filtration separation membranes made of ceramics such as alumina, silica and zeolite. Furthermore, it is possible to use an easily available and inexpensive alumina raw material powder, and control the average particle size and particle size distribution of the particles in the pulverized / dispersed slurry prepared by adding a sintering aid to the raw material powder. It is industrially very useful because it can be produced by the method of
以下、上記本発明の各構成要件について説明する。
・要件（ａ）について
本発明では、Ａｌ２Ｏ３の含有量を８３．０～９４．０重量％とする必要がある。好ましくは８５．０～９２．０重量％である。含有量が８３．０重量％未満では、ＳｉＯ２やアルカリ金属酸化物及びアルカリ土類金属酸化物量が増加し、ガラス相を多く形成するため焼結性が焼成温度に敏感となり、気孔率が低くなるし貫通気孔径も小さくなる。また、アルミナ結晶粒子界面にガラス相及び／又は第２相が多く形成されるため、機械的特性や耐食性の低下をきたす上に気孔径分布が広くなる。
一方、含有量が９４．０重量％を越えると、アルミナ以外のガラス相を形成する材料であるＳｉＯ２やアルカリ金属酸化物及びアルカリ土類金属の酸化物の含有量が少なくなるため、アルミナ結晶粒子界面のガラス相の量が少なくなり焼結性が低下する。そのため、所定の気孔率にするには焼成温度を高くする必要があるが、ガラス相が少ないため、気孔率及び気孔径を制御し難くなり、得られた基体管の貫通気孔のモード径が小さくなってしまう。また、アルミナ結晶同士の結合強度が低くなるため機械的特性が低下する。
Each component of the present invention will be described below.
· Regarding requirement (a) In the present invention, the content of Al 2 O 3 must be 83.0 to 94.0% by weight. It is preferably 85.0 to 92.0% by weight. If the content is less than 83.0% by weight, the amount of SiO 2 and alkali metal oxides and alkaline earth metal oxides increases, and a large amount of glass phase is formed, so the sinterability becomes sensitive to the firing temperature, and the porosity is low. In addition, the through pore diameter is also reduced. In addition, since a large amount of the glass phase and/or the second phase is formed at the interface between the alumina crystal grains, the mechanical properties and corrosion resistance are deteriorated, and the pore size distribution is widened.
On the other hand, if the content exceeds 94.0% by weight, the content of SiO2 , alkali metal oxides, and alkaline earth metal oxides, which are materials that form the glass phase other than alumina, decreases, so alumina crystals The amount of the glass phase at the particle interface is reduced and the sinterability is lowered. Therefore, it is necessary to raise the firing temperature in order to obtain a predetermined porosity. turn into. In addition, since the bonding strength between alumina crystals is low, the mechanical properties are degraded.
・要件（ｂ）について
本発明では、ＳｉＯ２含有量を５．０～１４．０重量％、アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量を１．０～３．５重量％、「ＳｉＯ２含有量／アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量」（ＳｉＯ２含有量と、アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量の比）を２．０～６．０とする必要がある。
好ましくはＳｉＯ２含有量が５．０～１１．０重量％、アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量が１．０～３．０重量％、「ＳｉＯ２含有量／アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量」が２．５～５．５である。
ＳｉＯ２含有量並びにアルカリ金属酸化物及びアルカリ土類金属酸化物の含有量だけでなく、「ＳｉＯ２含有量／アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量」も前記範囲内とすることにより、形成されるガラス相量及びガラス相の粘性が適正化され、本発明の範囲内の気孔率、気孔径及び気孔径分布を有する基体管を得ることができる。
なお、アルカリ金属酸化物及びアルカリ土類金属酸化物は珪石、長石、粘土等の形態で添加することが好ましい。
・Regarding the requirement (b) In the present invention, the content of SiO 2 is 5.0 to 14.0% by weight, the content of alkali metal oxides and alkaline earth metal oxides is 1.0 to 3.5% by weight, "SiO 2 content / content of alkali metal oxides and alkaline earth metal oxides" (ratio of SiO 2 content and content of alkali metal oxides and alkaline earth metal oxides) to 2.0 It should be 6.0.
Preferably, the SiO 2 content is 5.0 to 11.0% by weight, the content of alkali metal oxides and alkaline earth metal oxides is 1.0 to 3.0% by weight, "SiO 2 content/alkali metal The content of oxides and alkaline earth metal oxides” is 2.5 to 5.5.
Not only the SiO2 content and the content of alkali metal oxides and alkaline earth metal oxides, but also the " SiO2 content/content of alkali metal oxides and alkaline earth metal oxides" are within the above ranges. As a result, the amount of the glass phase formed and the viscosity of the glass phase are optimized, and a substrate tube having a porosity, pore diameter and pore diameter distribution within the scope of the present invention can be obtained.
The alkali metal oxides and alkaline earth metal oxides are preferably added in the form of silica, feldspar, clay or the like.
・要件（ｃ）について
本発明では気孔率を３０～５０％とする必要がある。好ましくは３５～４５％である。気孔率が３０％未満では貫通気孔量が低下し濾過分離能力の低下をきたす。一方、気孔率が５０％を越えると粗大気孔が増加し易くなり、機械的特性の低下や基体管への無機濾過分離膜の製膜性の低下をきたし、均一な膜を製膜しにくくなる。
なお、気孔率の測定はアルキメデス法（ＪＩＳ Ｒ １６３４に準拠）で行う。
- Requirement (c) In the present invention, the porosity must be 30 to 50%. Preferably it is 35-45%. If the porosity is less than 30%, the amount of through pores is reduced, resulting in reduced filtration and separation performance. On the other hand, if the porosity exceeds 50%, the number of coarse pores tends to increase, resulting in deterioration in mechanical properties and deterioration in the ability to form an inorganic filtration separation membrane on a substrate tube, making it difficult to form a uniform membrane. .
The porosity is measured by the Archimedes method (according to JIS R 1634).
・要件（ｄ）について
本発明ではバブルポイント法で測定した貫通気孔のモード径［要件（ｄ）などにおいて「モード径」と略すこともある］を０．２０～０．６０μｍとする必要がある。好ましくは０．３０～０．５０μｍである。モード径が０．２０μｍ未満では、製膜後のフィルターとしての濾過分離サイズは小さくなるが、濾過分離能力の低下をきたす。一方、モード径が０．６０μｍを越えると、濾過分離能力は向上するが基体管に製膜した無機濾過分離膜の均一性が低下し、その結果、濾過分離性能のバラツキが発生する。
なお、上記モード径は、ＡＳＴＭ Ｆ３１６－７０に準拠し、媒体としてフッ素系不活性溶液を用いて測定する。
・Regarding requirement (d) In the present invention, the mode diameter of through pores measured by the bubble point method [sometimes abbreviated as "mode diameter" in requirement (d), etc.] must be 0.20 to 0.60 μm. . It is preferably 0.30 to 0.50 μm. If the mode diameter is less than 0.20 μm, the filtration separation size as a filter after membrane formation is small, but the filtration separation ability is lowered. On the other hand, if the mode diameter exceeds 0.60 μm, the filtration separation ability is improved, but the uniformity of the inorganic filtration separation membrane formed on the substrate tube is reduced, resulting in variations in filtration separation performance.
The mode diameter is measured using a fluorine-based inert solution as a medium in accordance with ASTM F316-70.
・要件（ｅ）について
本発明では、バブルポイント法で測定した最大貫通気孔径、最小貫通気孔径、及び貫通気孔のモード径について、最大貫通気孔径／モード径が５．０以下、かつ、最小貫通気孔径／モード径が０．５以上とする必要がある。最大貫通気孔径／モード径は、好ましくは４．０以下であり、最小貫通気孔径／モード径は、好ましくは０．６以上である。最大貫通気孔径／モード径が５．０を越える場合及び／又は最小貫通気孔径／モード径が０．５未満の場合は、貫通気孔径分布が広いことになり、無機濾過分離膜を製膜したフィルター全体の濾過分離能力は高くなるが、貫通気孔径が大きい箇所と小さい箇所で膜厚や膜密度にバラツキが生じ、結果的にフィルターの各部分での濾過分離能力にバラツキが生じて、安定した濾過分離能力を得ることができない。なお、本発明のような安価な原料粉体を用いて粉砕・分散スラリー中の粒子の平均粒子径や粒度分布を制御する方法では、最大貫通気孔径／モード径の下限は２．０、最小貫通気孔径／モード径の上限は０．９程度である。
・Regarding requirement (e) In the present invention, regarding the maximum through-pore diameter, the minimum through-pore diameter, and the through-pore mode diameter measured by the bubble point method, the maximum through-pore diameter/mode diameter is 5.0 or less, and the minimum The through pore diameter/mode diameter should be 0.5 or more. The maximum through pore diameter/mode diameter is preferably 4.0 or less, and the minimum through pore diameter/mode diameter is preferably 0.6 or more. When the maximum through-pore diameter/mode diameter exceeds 5.0 and/or when the minimum through-pore diameter/mode diameter is less than 0.5, the through-pore diameter distribution is wide, and an inorganic filtration separation membrane is formed. Although the filtration and separation ability of the entire filter is increased, variations in film thickness and membrane density occur between areas with large and small through-pore diameters, resulting in variations in filtration and separation ability in each part of the filter. A stable filtration separation ability cannot be obtained. In the method of controlling the average particle size and particle size distribution of the particles in the pulverized/dispersed slurry using an inexpensive raw material powder as in the present invention, the lower limit of the maximum through-pore diameter/mode diameter is 2.0, and the minimum is 2.0. The upper limit of the through pore diameter/mode diameter is about 0.9.
・要件（ｆ）について
本発明では、基体管断面における直径３０～８０μｍの粗大気孔を５個／ｍｍ２以下とする必要がある。更に２０～８０μｍの粗大気孔が５個／ｍｍ２以下であることが好ましく、３個／ｍｍ２以下であることがより好ましい。
基体管断面に粗大気孔があると、無機濾過分離膜を製膜した際に粗大気孔がある部分と無い部分で膜厚が変化し、フィルターの各部で濾過分離能力にバラツキが発生しやすくなり、濾過分離能力の安定性を欠くことになる。
なお、粗大気孔は基体管断面を研磨して鏡面仕上げを行った後、走査電子顕微鏡により５００倍の倍率で観察して写真撮影し、画像面積１ｍｍ×１ｍｍにおける２０～８０μｍ又は３０～８０μｍの数を計測する。
·Regarding Requirement (f) In the present invention, the number of coarse pores with a diameter of 30 to 80 μm in the cross section of the substrate tube must be 5/mm 2 or less. Furthermore, the number of coarse pores of 20 to 80 μm is preferably 5/mm 2 or less, more preferably 3/mm 2 or less.
If there are coarse pores in the cross section of the base tube, the thickness of the inorganic filtration separation membrane will change between portions with coarse pores and portions without coarse pores when the inorganic filtration separation membrane is formed. It lacks the stability of the filtration separation ability.
After mirror-finishing the cross section of the substrate tube, the coarse pores were observed with a scanning electron microscope at a magnification of 500 times and photographed. to measure
・要件（ｇ）について
本発明では、液圧０．１ＭＰａで透水させた時の純水透過流束を３０～６０ｍ３／ｍ２／ｄａｙとする必要がある。好ましくは３５～５５ｍ３／ｍ２／ｄａｙである。純水透過流束が３０ｍ３／ｍ２／ｄａｙ未満の場合は濾過分離能力が低下し、フィルターとしての能力を発揮できない。一方、純水透過流束が６０ｍ３／ｍ２／ｄａｙを越えると、気孔率が高くなったり、気孔径が大きくなったり、気孔径分布が広くなったりして、濾過分離性能が低下する。また、気孔径が大きくなったり、気孔径分布が広くなると、基体管表面に製膜した膜の均一性が低下するため、濾過分離膜の性能の低下につながる。
上記純水透過流束は、外径φ１２ｍｍ、内径φ９ｍｍ、長さ１００ｍｍの基体管をサンプルとして用い、２５℃のイオン交換水により０．１ＭＰａの液圧をかけた時の時間当たりの透水量と基体管の表面積に基づいて、下式により求めることができる。
The pure water permeation flux is calculated by using a substrate tube with an outer diameter of φ12 mm, an inner diameter of φ9 mm, and a length of 100 mm as a sample, and applying a liquid pressure of 0.1 MPa with ion-exchanged water at 25 ° C. It can be obtained by the following formula based on the surface area of the substrate tube.
本発明のアルミナ質基体管は以下に示す方法で製造できる。
製造に際しては、原料粉体の粉砕・分散スラリー中の粒子の粒度分布を精密に制御することによって、貫通気孔のモード径が特定の範囲になるようにすること、及び最大貫通気孔径と最小貫通気孔径をモード径に対して特定の範囲内に制御することにより、貫通気孔径分布をシャープにすることが重要である。これにより、高い濾過分離能力に加えて、従来は基体管の濾過分離性能として殆ど指摘されていなかった濾過分離能力の圧力依存性及び短時間で濾過量を安定にさせるという特性を付与することができる。その結果、優れた製膜性及び濾過分離特性を有するアルミナ質基体管が得られる。
The alumina substrate tube of the present invention can be manufactured by the method shown below.
During production, by precisely controlling the particle size distribution of the particles in the pulverized and dispersed slurry of the raw material powder, the mode diameter of the through pores is set to a specific range, and the maximum and minimum through pore diameters are controlled. It is important to sharpen the through pore size distribution by controlling the pore size within a specific range with respect to the mode size. As a result, in addition to high filtration and separation performance, it is possible to impart the pressure dependence of filtration and separation performance, which has been hardly pointed out as the filtration and separation performance of the substrate tube, and the characteristic of stabilizing the filtration amount in a short time. can. As a result, an aluminous substrate tube having excellent film formability and filtration separation properties can be obtained.
本発明ではアルミナ純度９９重量％以上、好ましくは９９．５重量％以上で平均粒子径４～７μｍ、好ましくは５～７μｍのアルミナ原料粉体を用いる。原料粉体としては種々の製法で製造されたものを使用できるが、バイヤー法によるものが安価で好ましい。
アルミナ純度が９９重量％未満の場合は基体管が含有する不純物量が多くなり、アルミナ結晶粒界に形成されるガラス相及び／又は第２相が多くなって、基体管の機械的特性等の低下を招く。また、平均粒子径が４μｍ未満の場合は焼結性が高くなるため、焼結体密度が焼成温度に敏感となり、気孔率及び気孔径を制御し難くなる。一方、平均粒子径が７μｍを越えると粉砕・分散し難くなり、ひいては焼成した基体管の気孔径が大きくなり易い。
また、焼結助剤として添加するＳｉＯ２、アルカリ金属酸化物及びアルカリ土類金属酸化物は、珪石、長石、粘土等の原料粉体の形態で添加する方がアルミナ原料粉体中に分散・混合し易いため好ましい。前記原料粉体の平均粒子径は０．５～５μｍとするが、好ましくは０．５～３μｍである。平均粒子径が０．５μｍ未満では分散し難くなり、アルミナ原料粉体中に均一に混合できなくなるし、５μｍを越えると、アルミナ結晶粒界に形成されるガラス相の組成の均一性が低下すると共にアルミナ結晶粒界に存在するガラス相の大きさにもバラツキが生じ、結果として、気孔径分布が広くなったり、濾過分離時にフィルター供給する液体や気体の圧力依存性が大きくなったり、濾過分離が安定しない原因となる。
In the present invention, an alumina raw powder having an alumina purity of 99% by weight or more, preferably 99.5% by weight or more and an average particle size of 4 to 7 μm, preferably 5 to 7 μm is used. As raw material powders, those produced by various production methods can be used, but those produced by the Bayer method are preferable because they are inexpensive.
If the alumina purity is less than 99% by weight, the amount of impurities contained in the substrate tube increases, and the amount of glass phase and/or second phase formed at the alumina crystal grain boundary increases, resulting in poor mechanical properties of the substrate tube. lead to decline. Moreover, when the average particle size is less than 4 μm, the sinterability is high, so the density of the sintered body becomes sensitive to the firing temperature, making it difficult to control the porosity and pore size. On the other hand, if the average particle size exceeds 7 μm, it becomes difficult to pulverize and disperse, and the pore size of the fired substrate tube tends to increase.
Further, SiO 2 , alkali metal oxides and alkaline earth metal oxides added as sintering aids are preferably added in the form of raw material powders such as silica, feldspar, and clay to disperse and disperse in alumina raw material powders. It is preferable because it is easy to mix. The raw material powder has an average particle size of 0.5 to 5 μm, preferably 0.5 to 3 μm. If the average particle size is less than 0.5 μm, it becomes difficult to disperse it and cannot be uniformly mixed in the raw alumina powder. At the same time, the size of the glass phase existing at the alumina crystal grain boundary also varies, resulting in a wide pore size distribution, a large pressure dependence of the liquid or gas supplied to the filter during filtration separation, and a causes instability.
以上の原料を所定の組成及び重量比になるように配合し、湿式でポットミルやアトリッションミル等により、水を溶媒として粉砕・分散しスラリーとする。スラリー中の粒子の平均粒子径及び粒度分布は、粉砕・分散時の粉体濃度、分散剤の種類及び添加量、使用するボールサイズ及び充填量、処理時間を調整してコントロールする。
スラリー中の粒子の平均粒子径は３．０～５．０μｍ、好ましくは３．５～４．５μｍとする。平均粒子径が３．０μｍ未満では焼結性が高くなり、形成される気孔径が小さくなり過ぎる。一方、平均粒子径が５．０μｍを越えると粒子径分布が広くなり、粗大気孔が多くなったり気孔径分布が広くなったりして濾過性能の低下につながる。なお、本発明のような安価な原料粉体を用いて粉砕・分散スラリー中の粒子の平均粒子径や粒度分布を制御する方法では３．０μｍ程度が下限である。
上記平均粒子径は体積基準で粒度分析を行って累積が５０％になった時の粒子径であるが、粒度分析の測定にはマイクロトラックベル社（旧日機装社）製のマイクロトラック ＭＴ３０００を使用する。
また、スラリー中の粒子の粒度分布も貫通気孔径及びその分布を制御する上で重要であり、粒子径の累積が９０％の時の粒子径：Ｄ９０と、１０％の時の粒子径：Ｄ１０との差を５以下とする必要がある。差が５を越えると粒子径分布が広くなり充填性が向上するので、得られる基体管の貫通気孔のモード径は本発明の範囲内にできるが、十分に焼結しないため閉気孔として粗大気孔が残り易くなり好ましくない。
The above raw materials are blended so as to have a predetermined composition and weight ratio, and are pulverized and dispersed using water as a solvent by a wet process such as a pot mill or an attrition mill to obtain a slurry. The average particle size and particle size distribution of the particles in the slurry are controlled by adjusting the powder concentration during pulverization and dispersion, the type and amount of dispersant added, the ball size and filling amount used, and the treatment time.
The average particle size of the particles in the slurry is 3.0-5.0 μm, preferably 3.5-4.5 μm. If the average particle size is less than 3.0 μm, the sinterability becomes high and the pore size formed becomes too small. On the other hand, if the average particle size exceeds 5.0 μm, the particle size distribution becomes wide, and the coarse pores increase or the pore size distribution widens, leading to a decrease in filtration performance. In the method of controlling the average particle size and particle size distribution of the particles in the pulverized/dispersed slurry using an inexpensive raw material powder as in the present invention, the lower limit is about 3.0 μm.
The above average particle diameter is the particle diameter when the particle size analysis is performed on a volume basis and the accumulation reaches 50%. Microtrac MT3000 manufactured by Microtrac Bell Co., Ltd. (former Nikkiso Co., Ltd.) is used for the measurement of the particle size analysis. do.
In addition, the particle size distribution of the particles in the slurry is also important in controlling the through pore size and its distribution. should be 5 or less. If the difference exceeds 5, the particle size distribution will be widened and the packing property will be improved. Therefore, the mode diameter of the through pores of the substrate tube to be obtained can be within the range of the present invention. is likely to remain, which is not preferable.
本発明の基体管は、上記スラリーを用いて種々の方法で成形することにより作製する。
例えば押出成形を採用する場合は、前記スラリーを乾燥・整粒し、これに公知の押出成形用バインダー（カルボキシルメチルセルロース、ワックスエマルジョン等）と水を加えて混合し、土練をして成形坏土とした後、所定の形状になるように成形する。
また、プレス成形を採用する場合は、前記スラリーに公知のバインダー（ワックスエマルジョン、ＰＶＡ、アクリル樹脂等）を添加し、スプレードライヤーで乾燥させて成形用粉体を作製し、型を用いて成形する。
なお、従来の基体管は気孔を多く形成するためバインダーと一緒に気孔形成剤を添加する場合が多いが、本発明では気孔形成剤を添加すると気孔径サイズが大きくなったり気孔径分布が広くなって、気孔径分布の制御が難しくなるので添加しない。
得られた成形体を１２５０～１５００℃、好ましくは１３００～１４５０℃で焼成すれば本発明の基体管を作製することができる。
The substrate tube of the present invention is produced by molding by various methods using the above slurry.
For example, when extrusion molding is employed, the slurry is dried and granulated, and a known binder for extrusion molding (carboxymethyl cellulose, wax emulsion, etc.) and water are added and mixed, and kneaded to form a molding clay. After that, it is molded into a predetermined shape.
When press molding is employed, a known binder (wax emulsion, PVA, acrylic resin, etc.) is added to the slurry, dried with a spray dryer to prepare molding powder, and molded using a mold. .
A pore-forming agent is often added together with a binder in order to form a large number of pores in a conventional substrate tube. Therefore, it is difficult to control the pore size distribution, so it is not added.
The substrate tube of the present invention can be produced by sintering the obtained compact at 1250 to 1500°C, preferably at 1300 to 1450°C.
以下、実施例及び比較例を示して本発明を更に具体的に説明するが、本発明はこれらの実施例により何ら限定されるものではない。尚、例中の「％」は気孔率を除き「重量％」である。 EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. "%" in the examples means "% by weight" except for porosity.
実施例１～８、比較例１～９
純度９９．５％、平均粒子径５．３μｍの市販のアルミナ原料粉体に対し、平均粒子径１．３μｍに粉砕した長石及び平均粒子径１．８μｍの木節粘土を、表１の各実施例及び比較例の欄に示す組成になるように配合し、水を用いて湿式で１２時間粉砕・分散してスラリーとした後、乾燥させて粉体を得た。
また、比較例１では純度９９．９％、平均粒子径３．２μｍの市販のアルミナ原料粉体を使用し、比較例２では、純度９９．５％、平均粒子径５．３μｍの市販のアルミナ原料粉体と比較例１と同じアルミナ原料粉体を５０％ずつ混合したものを使用した。更に比較例８では粉砕・分散時間を６時間とした。
粉砕・分散したスラリー中の粒子の平均粒子径及び粒子径の累積が９０％の時の粒子径：Ｄ９０と１０％の時の粒子径：Ｄ１０との差を表１に示す。
次いで得られた粉体にバインダーのメチルセルロースと水を添加し、混合・混練・土練をして押出成形用坏土を作製した。また、比較例４では更に気孔形成剤を５％添加した。
次いで得られた押出成形用坏土を用いて押出成形し、１２１０～１５８０℃で焼成して外径がφ１２ｍｍ、内径が９ｍｍ、長さが１００ｍｍのアルミナ質基体管を作製した。
Examples 1-8, Comparative Examples 1-9
Feldspar pulverized to an average particle size of 1.3 μm and Kibushi clay having an average particle size of 1.8 μm were added to commercially available alumina raw powder having a purity of 99.5% and an average particle size of 5.3 μm, and The mixture was blended so as to have the composition shown in the columns of Examples and Comparative Examples, wet pulverized and dispersed with water for 12 hours to form a slurry, and then dried to obtain a powder.
Further, in Comparative Example 1, a commercially available alumina raw material powder having a purity of 99.9% and an average particle size of 3.2 μm was used, and in Comparative Example 2, a commercially available alumina having a purity of 99.5% and an average particle size of 5.3 μm was used. A mixture of 50% each of the raw material powder and the same alumina raw material powder as in Comparative Example 1 was used. Furthermore, in Comparative Example 8, the pulverization/dispersion time was set to 6 hours.
Table 1 shows the average particle size of the particles in the pulverized and dispersed slurry and the difference between the particle size D90 when the cumulative particle size is 90% and the particle size D10 when the cumulative particle size is 10%.
Next, methyl cellulose as a binder and water were added to the obtained powder, and the mixture was mixed, kneaded, and kneaded to prepare a clay for extrusion molding. Also, in Comparative Example 4, 5% of a pore forming agent was added.
Then, the obtained extrusion molding clay was extruded and sintered at 1210 to 1580° C. to produce an alumina base tube having an outer diameter of φ12 mm, an inner diameter of 9 mm and a length of 100 mm.
表２に、各基体管について、前述した方法で求めた各特性、及び以下の方法で測定した純水透過流束に対する液圧依存性と純水透過流束が安定するまでの時間を示す。
純水透過流束に対する液圧依存性は、各基体管に２５℃のイオン交換水を使用して液圧０．０１５～０．１ＭＰａをかけた時に次式から得られるａの値（液圧依存係数）により評価した。式中のＬは純水透過流束、Ｐは液圧、ａは式の傾きである。
Ｌ（ｍ３／ｍ２／ｄａｙ）＝ａ×Ｐ（ＭＰａ）＋ｂ
また、純水透過流束が安定するまでの時間は、上記と同じ方法により液圧０．１ＭＰａで透水させた時に、時間当たりの透水量が一定になるまでの時間（秒）により評価した。
Table 2 shows the characteristics obtained by the method described above, the hydraulic pressure dependence of the pure water permeation flux measured by the following method, and the time required for the pure water permeation flux to stabilize for each substrate tube.
The hydraulic pressure dependence of the pure water permeation flux is the value of a (hydraulic pressure dependence coefficient). In the formula, L is the pure water permeation flux, P is the hydraulic pressure, and a is the slope of the formula.
L (m 3 /m 2 /day) = a x P (MPa) + b
The time required for the pure water permeation flux to stabilize was evaluated by the time (seconds) required for the water permeation rate to become constant when water was permeated at a liquid pressure of 0.1 MPa by the same method as above.
表２から判るように、本発明の要件を全て満たす基体管は、純水透過流束に対する液圧依存係数が４００～５００、純水透過流束が安定するまでの時間が１０～３０秒であり、優れた濾過分離性能を有している。液圧依存係数が５００を越えると、基体管に無機濾過分離膜を製膜したフィルターで濾過分離を行った際のフィルターへの供給圧力が高くなり、安定した濾過分離ができなくなったりフィルターの破損等を生じるので好ましくない。
また、純水透過流束が安定するまでの時間が３０秒を越えると、フィルターの断続運転が難しくなったり、短時間運転の安定性が低下するので好ましくない。
As can be seen from Table 2, the base tube satisfying all the requirements of the present invention has a hydraulic pressure dependence coefficient of 400 to 500 with respect to the pure water permeation flux, and a stabilization time of 10 to 30 seconds for the pure water permeation flux. It has excellent filtration separation performance. If the hydraulic pressure dependence coefficient exceeds 500, the supply pressure to the filter becomes high when performing filtration separation with a filter having an inorganic filtration separation membrane formed on the substrate tube, and stable filtration separation becomes impossible or the filter is damaged. etc. is not preferable.
On the other hand, if the time until the pure water permeation flux is stabilized exceeds 30 seconds, intermittent operation of the filter becomes difficult and the stability of short-time operation decreases, which is not preferable.
表１、表２において比較例１～９が示す技術的意義は以下のとおりである。
比較例１：所定よりも平均粒子径が小さいアルミナ原料粉体を用いたため、粉砕・分散スラリー中の粒子の平均粒子径が所定の数値範囲よりも小さくなり、焼結性が高くなって気孔率が低く、純水透過流束も低くなり、その結果、液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例２：平均粒子径が異なる２種類のアルミナ原料粉体を用いたため、粉砕・分散スラリー中の粒子の粒度分布が広くなり、形成される気孔径分布が広くなり、同時に粗大気孔が残り、結果的に液圧依存係数について十分な特性が得られなかった例である。
比較例３：アルミナ含有量が規定範囲より少ないことにより、ＳｉＯ２含有量が多くなり、ガラス相量が増え、焼結が進み、気孔率及び純水透過流束が規定範囲よりも小さくなり、液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例４：押出成形用坏土に気孔形成剤を添加した結果、形成される気孔径が大きくなり、最大貫通気孔径／モード径が規定範囲を超えて気孔径分布が広くなってしまい、液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例５：「ＳｉＯ２含有量／アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量」が規定範囲より大きいため、ガラス相の粘性が適正化されず、気孔径制御がしにくくなり、結果として、純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例６：アルミナ含有量が規定範囲より多いためアルミナ結晶粒子界面のガラス相量が少なくなって焼結性が低下し、その結果、気孔径の制御ができず、貫通気孔のモード径が既定値より小さくなって、液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例７：アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量が規定範囲よりも多いため、焼成時に形成されるガラス相の粘性を適正化できず、その結果、気孔径の制御ができなくて、最小貫通気孔径／モード径が規定範囲よりも小さくなり、液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例８：粉砕・分散粉体の平均粒子径及びＤ９０－Ｄ１０の数値が所定範囲より大きいため、焼結性が低くなり、気孔率を始め全ての基体管特性が規定範囲外となり液圧依存係数及び純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
比較例９：「ＳｉＯ２含有量／アルカリ金属酸化物及びアルカリ土類金属酸化物の含有量」が小さいため、焼成中に形成されるガラス相の粘性が最適化されず、気孔分布が広くなり、純水透過流束が安定するまでの時間について十分な特性が得られなかった例である。
The technical significance shown by Comparative Examples 1 to 9 in Tables 1 and 2 is as follows.
Comparative Example 1: Since an alumina raw material powder having an average particle size smaller than the predetermined value was used, the average particle size of the particles in the pulverized/dispersed slurry was smaller than the predetermined numerical range, resulting in high sinterability and porosity. is low, the pure water permeation flux is also low, and as a result, sufficient characteristics were not obtained for the hydraulic pressure dependence coefficient and the time until the pure water permeation flux stabilizes.
Comparative Example 2: Since two types of alumina raw material powders having different average particle sizes were used, the particle size distribution of the particles in the pulverized/dispersed slurry was widened, the pore size distribution formed was widened, and at the same time coarse pores remained. This is an example in which, as a result, sufficient characteristics were not obtained for the hydraulic pressure dependence coefficient.
Comparative Example 3: The alumina content is less than the specified range, the SiO2 content is increased, the glass phase content is increased, sintering proceeds, the porosity and pure water permeation flux are smaller than the specified range, This is an example in which sufficient characteristics were not obtained for the hydraulic pressure dependence coefficient and the time required for the pure water permeation flux to stabilize.
Comparative Example 4: As a result of adding a pore-forming agent to the extrusion molding clay, the pore diameters formed increased, the maximum through pore diameter/mode diameter exceeded the specified range, and the pore diameter distribution widened. This is an example in which sufficient characteristics were not obtained with respect to the pressure dependence coefficient and the time until the pure water permeation flux stabilized.
Comparative Example 5: Since the "SiO 2 content/content of alkali metal oxides and alkaline earth metal oxides" is larger than the specified range, the viscosity of the glass phase is not optimized, making it difficult to control the pore diameter. As a result, this is an example in which sufficient characteristics were not obtained with respect to the time required for the pure water permeation flux to stabilize.
Comparative Example 6: Since the alumina content is higher than the specified range, the amount of glass phase at the interface of alumina crystal grains is reduced and the sinterability is lowered. This is an example in which sufficient characteristics were not obtained with respect to the time required for the hydraulic pressure dependence coefficient and pure water permeation flux to stabilize.
Comparative Example 7: Since the content of alkali metal oxides and alkaline earth metal oxides is higher than the specified range, the viscosity of the glass phase formed during firing cannot be optimized, and as a result, the pore diameter cannot be controlled. This is an example in which the minimum through pore diameter/mode diameter became smaller than the specified range, and sufficient characteristics were not obtained with respect to the time required for the hydraulic pressure dependence coefficient and the pure water permeation flux to stabilize.
Comparative Example 8: Since the average particle size of the pulverized/dispersed powder and the value of D90-D10 are larger than the predetermined range, the sinterability is low, and all the properties of the substrate tube including the porosity are outside the specified range and dependent on the liquid pressure. This is an example in which sufficient characteristics were not obtained with respect to the coefficient and the time until the pure water permeation flux stabilized.
Comparative Example 9: Due to the small " SiO2 content/content of alkali metal oxides and alkaline earth metal oxides", the viscosity of the glass phase formed during firing is not optimized and the pore distribution is broadened. , in which sufficient characteristics were not obtained for the time until the pure water permeation flux was stabilized.
また、図１として実施例５と比較例２の基体管の断面を鏡面仕上げして走査電子顕微鏡で観察した写真を示す。
両者を対比すると、比較例２では幾つかの大きな気孔が散見されるが（代表的なものを○で囲って示した）、実施例５には、比較例２のような大きな気孔は全く見られない。
上記したように、表１～表２及び図１に示した結果から、本発明のアルミナ質基体管は優れた製膜性及び濾過分離特性を有することが分かる。
Also, FIG. 1 shows photographs of mirror-polished cross-sections of the substrate tubes of Example 5 and Comparative Example 2, which were observed with a scanning electron microscope.
Comparing the two, in Comparative Example 2, some large pores are observed (representative ones are circled), but in Example 5, no large pores like those in Comparative Example 2 are observed. can't
As described above, from the results shown in Tables 1 and 2 and FIG. 1, it can be seen that the alumina substrate tube of the present invention has excellent film forming properties and filtration separation properties.
Claims (1)
（ａ）Ａｌ２Ｏ３の含有量が８３．０～９４．０重量％
（ｂ）ＳｉＯ２の含有量が５．０～１４．０重量％、アルカリ金属酸化物及びアルカリ
土類金属酸化物の含有量が１．０～３．５重量％、「ＳｉＯ２含有量／アルカリ
金属酸化物及びアルカリ土類金属酸化物の含有量」が２．０～６．０
（ｃ）気孔率が３０～５０％
（ｄ）バブルポイント法で測定した貫通気孔のモード径が０．２０～０．６０μｍ
（ｅ）バブルポイント法で測定した最大貫通気孔径／モード径が５．０以下、
かつ、最小貫通気孔径／モード径が０．５以上
（ｆ）基体管断面における直径３０～８０μｍの粗大気孔が５個／ｍｍ２以下
（ｇ）液圧０．１ＭＰａで透水させた時の純水透過流束が３０～６０ｍ３／ｍ２／ｄａ
ｙ
An aluminous substrate tube for a filter using an inorganic filtration separation membrane, characterized by satisfying the following requirements (a) to (g).
(a) Al 2 O 3 content is 83.0 to 94.0% by weight
(b) the content of SiO 2 is 5.0-14.0% by weight, the content of alkali metal oxides and alkaline earth metal oxides is 1.0-3.5% by weight, "SiO 2 content/ The content of alkali metal oxides and alkaline earth metal oxides” is 2.0 to 6.0
(c) Porosity is 30 to 50%
(d) The mode diameter of through pores measured by the bubble point method is 0.20 to 0.60 μm
(e) the maximum through-hole diameter/mode diameter measured by the bubble point method is 5.0 or less;
and the minimum through pore diameter/mode diameter is 0.5 or more (f) The number of coarse pores with a diameter of 30 to 80 μm in the cross section of the substrate tube is 5/mm 2 or less Water permeation flux is 30-60m 3 /m 2 /da
y
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